Samoans will have to start paying a hefty fee to fly on Samoa Air if they're overweight.

Samoa Air is the first airline to make customers pay as much as they weigh when flying on the airline. For overweight customers, this could mean big charges.

"This is the fairest way of travelling," said Chris Langton, chief executive of Samoa Air. "There are no extra fees in terms of excess baggage or anything – it is just a kilo is a kilo is a kilo."

Customers will have to start typing in their weight when purchasing Samoa Air tickets online, and pay anywhere from about $1 to about $4.16 per kilogram (depending on whether they're traveling short domestic routes or between Samoa and American Samoa).

Once arriving at the airport, the customers are weighed again to make sure they didn't lie online.

Why is Samoa Air doing this? According to Langton, it's partially meant to raise awareness of obesity and health, since Samoa is often in the top 10 lists for obesity.

"When you get into the Pacific, standard weight is substantially higher [than south-east Asia]," said Langton. "That's a health issue in some areas. [This payment system] has raised the awareness of weight."

The payment by weight system will have other benefits, such as safety measures where a plane can only handle so many overweight customers (larger passengers have to be evenly distributed on the plane for safety); families with young children could pay much less than what they're paying now, and carriers could gain the money lost on fuel for carrying heavier passengers.